Septal defects, holes in the septum dividing the right and left atria and right and left ventricles, are common congenital cardiac defects. Conventionally, such atrial and ventricular septal defects have been surgically corrected, requiring a thoracotomy and all of the attendant risks to the patient's health presented by open surgery.
In an attempt to overcome some of the risks attending surgical correction of septal defects, a number of percutaneously deliverable devices have been devised to seal cardiac septal defects. For example, U.S. Pat. No. 3,874,388 to King et al. describes a device comprising a pair of mechanically connected umbrella-like structures covered with a fluid impermeable material and having barbs that attach the device to the tissue surrounding the septal defect. The umbrella-like structures are closed for percutaneous delivery, and then expanded into position, one on either side of the tissue surrounding the defect, to close the hole.
U.S. Pat. No. 5,578,045 to Das, U.S. Pat. No. 5,192,301 to Kamiya et al., and U.S. Pat. No. 4,917,089 to Sideris all describe percutaneously medical hole closure devices having two closure members disposed on opposite sides of the hole and connected by a connecting member, such as a spring. These devices seek to seal a hole by holding the closure members tightly against the tissue adjacent to either side of the hole.
Previously known septal defect closure devices have a number of drawbacks. Foremost among these disadvantages is the inability of the devices to conform to the size of the septal defect. Such devices therefor require great care in placement, to ensure that the closure members entirely cover the hole. Because the previously known devices typically use expanding frames to support the closure members that can easily straddle the hole, or otherwise become caught, complications may arise during implantation of such devices.
Previously known devices also require that the closure members exert a high compressive contact force on either side of the tissue surrounding the hole. In many instances, there may be insufficient intact wall area surrounding the hole to permit placement of the closure members without interfering with other cardiac structures, such as the atrioventricular valves. The tissue surrounding a hole also may move, expand, or contract, during the cardiac cycle, making it difficult for the closure members to maintain a good seal, or the hole may deform over time.
In addition, the connecting member used to retain the closure members in intimate contact with the tissue surrounding the hole may experience stress relaxation and creep, phenomena whereby the connecting member loses its resiliency. The resulting loss in compressive contact force permits the closure members to leak. Previously known devices, such as described above, also present a risk of fatigue fracture under conditions commonly found in the heart.
It therefore would be desirable to provide apparatus and methods for percutaneously closing holes in the heart, and other tissue, in which the device conforms to the size of the hole.
It also would be desirable to provide apparatus and methods for percutaneously closing holes in the heart, and other tissue, in which the device may be easily deployed without complications associated with premature or mispositioned deployment of the closure members.
It further would be desirable to provide apparatus and methods for closing holes in the heart, and other tissue, which are able to seal a hole without requiring high compressive contact forces on tissue adjacent to the hole.
It yet further would be desirable to provide apparatus and methods for closing holes in the heart, and other tissue, which employ components that are not subjected to continual loading, and therefore present a low risk of leakage due to stress relaxation or fatigue fracture.